It is known to conduct fracturing or other treating procedures in a wellbore by isolating zones in the wellbore using packers and the like and subjecting the isolated zone to treatment fluids at treatment pressures. In a typical fracturing procedure, for example, the casing of the well is perforated to admit oil and/or gas from the formation into the well and fracturing fluid is then pumped into the well and through these perforations into the formation. Such treatment opens and/or enlarges draining channels in the formation, enhancing the producing ability of the well. Alternatively, the completion can be an open hole type that is completed without casing in the producing formation area.
It is desired to stimulate multiple zones, or intervals within the same zone, using onsite stimulation fluid pumping equipment (pumpers). A packer arrangement is inserted at intervals isolating one zone from an adjacent zone. It is known to introduce a drop ball through the wellbore to engage one of the packers (or packer interval) in order to block fluid flow therethrough. Passage through a downhole packer is thereby plugged off with this drop ball that is pumped into the wellbore during the stimulation flush. The drop ball blocks off this downhole packer, isolating the wellbore uphole of the downhole packer and consequently a second zone, above this downhole packer, can be stimulated. Once stimulated, a subsequent drop ball can be dropped to block off a subsequent packer uphole of the blocked packer for stimulation thereabove. This continues until all the desired zones are stimulated.
At surface, the wellbore is generally furnished with a frachead unit including a multi-port block or a Y-type frac header, isolation tool or the like, which provides fluid connections for introducing stimulation fluids including sand, gels and acid treatments.
After well operations, fluid from the well is flowed to surface through the wellhead or frachead. The fluid is urged from the well such as under formation pressures and/or the influence of a gaseous charge of CO2 or N2. The fluid from the well exits the wellhead from a horizontally extending fitting. To separate the balls from the fluid, it is known to use a cross fitting apparatus such as a plate extending across the flow path from the wellhead. The plate is typically a plate across the flow path having large slots or screen at the face such as an upside down “U” or fork shape for impeding balls recovered with the fluid while permitting fluid to flow therethrough the “U” shape.
It is known for balls, of which various sizes are employed in one well operation, to become lodged at the prior art U-shape or screen and block fluid flow. In other instances, the balls can break apart which encourages further blockages.
During maximum flow back operations involving wellbore fluids containing sand, stagnation of the wellbore fluids in the ball catcher and related apparatus can cause the sand entrained therein to settle and rapidly accumulate, interfering with ball catcher performance. Failure of the ball catcher can result in wellbore plugging and other complications.
Therefore, there is a need for a more effective apparatus for retrieving balls from wellbore fluids containing sand after a well operation.